While I agree that there is no level requirement for RP, worshipping all the gods (or even simply refusing to revere one above all the others) comes with its benefits and drawbacks.
Benefits include:
- freedom of roleplay to whatever standard you desire
- ability to use pantheist-only spells and armor
- as a priest, ability to wear armor types that may be restricted after you choose a faith
Drawbacks include:
- Gods are (generally) apathetic to your character in turn. For priests, this means you have only the basic spells of a cleric. While you're certainly free to get to GM without being invested, there's no reason why you should have the benefit that devoted priests and priestesses have during that journey.
- No access to sacred items or spells -- tying in with the above. These are reserved for followers.
Rewarding pantheism for a class that is specifically tied to religion is kind of silly, in my opinion. Very few characters have ever been true pantheists that "worship" all of the gods. Most pantheist types worship the gods of light, darkness, natural forces or some other logical combination that fits their concept. It'd be fairly ridiculois for an elven priest, for example, to take on pantheism in a true sense. Unless you're grep, you're not going to bother trying to justify worshipping Thuban in part or in full as a light aura.
Even fewer characters are stupid enough to deny the existence of any of the gods. Since they're real, the pantheon is a reality of Pyrathia. Acknowledging all the gods is not the same as worshipping them.